The incorporation of lignocellulosic materials as a reinforcing component in polymer composites has received increased attention, particularly for price driven and high volume applications. This development reflects several advantages of lignocellulosic fibbers over their inorganic counterparts, including lower density, reduced abrasiveness to expensive moulds and mixing equipment, as well as being less expensive. Moreover, lignocellulosic based fibers are derived from renewable resources. The major challenge for natural fiber composites is their inherent poor adhesion between fiber and the matrix, high moisture absorption and UV degradation. Lignin and hemicelluloses are the components of natural fiber which are mostly responsible for moisture absorption and UV degradation. In this study, the lignocelluloses (Oil Palm Empty Fruit Bunch) were treated with alkaline peroxide to remove lignin and hemicelluloses. Composites were produced with treated and untreated fiber using up to 50% fiber with polypropylene (PP) matrix using twin-screw extruder followed by injection molding. Composites were characterized using tensile and flexural testing, SEM and TGA. The tensile and flexural modulus were found to be higher for alkaline peroxide treated fiber composites compared to untreated fiber composites. To improve interfacial bonding, additional of coupling agents also found to provide higher strength and modulus of composites. The treated fiber and their composites provided higher thermal stability compared to untreated fiber and their composites, respectively.